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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of change in estimated future development costs.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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No definition available.

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Description of fees associated with providing collateral for the credit facility.

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Amount of the fees associated with providing collateral for the credit facility.

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Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Indebtedness divided by net capital.

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Credit Facility - Additional Information (Detail)	1 Months Ended	3 Months Ended		6 Months Ended		15 Months Ended
Credit Facility - Additional Information (Detail)	Aug. 07, 2017	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2018 USD ($)	Jan. 11, 2017 USD ($)
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		2.16		2.16
Debt Instrument, Convertible, Conversion Ratio		5.41		5.41
Capital Expenditure limit		$ 27,500,000
Line of Credit Facility, Maximum Borrowing Capacity		92,100,000		$ 92,100,000
Change in construction cost estimates		(115,200,000)	$ (98,100,000)	$ (112,200,000)		$ 4,000,000
Line of Credit Facility Possible Increase in Capacity Leverage Ratio					200.00%
Line of Credit Facility, Collateral Fees				0.015
Line of Credit Facility, Collateral Fees, Amount				$ 1,500,000
Revolving debt		$ 131,398,000	24,041,000	$ 131,398,000
Debt Instrument, Interest Rate, Effective Percentage		3.80%		3.80%
Outstanding letter of credit		$ 273,300,000	255,200,000	$ 273,300,000
Guarantor Obligations, Current Carrying Value		$ 465,300,000		$ 465,300,000
Second Lien Term Loan Facility [Member]
Debt Instrument [Line Items]
Premium on voluntary prepayments made in the second year		0.00%
Debt Instrument, Fee		.005
Debt Instrument, Interest Rate, Effective Percentage	12.00%	0.00%		0.00%
Premium on voluntary prepayments in the third year		0.00%
New Credit Agreement
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 600,000,000
Line of Credit Facility Possible Increase in Capacity Amount					$ 200,000,000
Debt Instrument, Basis Spread on Variable Rate				5.00%
Revolving debt		$ 118,130,000	9,800,000	$ 118,130,000
Financial Letter of Credit outstanding [Domain]
Debt Instrument [Line Items]
Line of Credit Facility, Collateral Fees				0.025
Foreign Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		14,500,000		$ 14,500,000
Revolving debt		$ 13,268,000	$ 14,241,000	$ 13,268,000
Debt Instrument, Interest Rate, Effective Percentage		5.10%		5.10%
Universal [Member]
Debt Instrument [Line Items]
Revolving debt							$ 55,000,000
Credit Facility [Domain] \| New Credit Agreement
Debt Instrument [Line Items]
Line of Credit Facility Fee Percentage				0.50%
Minimum [Member]
Debt Instrument [Line Items]
Covenant terms, liquidity		$ 75,000,000.0		$ 75,000,000.0
Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Covenant Terms	500			600
Maximum [Member] \| New Credit Agreement
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate				4.00%
Quarter ended after September 30, 2017 [Domain] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio		1.50		1.50
Quarter ended after September 30, 2017 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		6.00		6.00
Quarter ended December 31, 2017 [Domain] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio		1.00		1.00
Quarter ended June 30, 2018 [Domain] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio		1.25		1.25
Quarter ended June 30, 2018 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		6.25		6.25
Quarters ended September 30, 2018 and December 31, 2018 [Domain] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio		1.50		1.50
Quarters ended December 31, 2017 and March 31, 2018 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		8.50		8.50
Quarter ended September 30, 2018 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		4.00		4.00
Quarter ended December 31, 2018 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		3.75		3.75
Quarters ended March 31, 2019 and June 30, 2019 [Domain] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio		1.75		1.75
Quarters ended March 31, 2019 and June 30, 2019 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		3.25		3.25
Quarters ended September 30, 2019 and thereafter [Domain] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio		2.00		2.00
Quarters ended September 30, 2019 and thereafter [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital		3.00		3.00
Allowed loss per Volund project during Q3 2017 [Domain] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description		25
Financial Standby Letter of Credit [Member] \| During Covenant Relief Period [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 30,000,000		$ 30,000,000
Amended Credit Agreement [Member] \| During Covenant Relief Period [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		250,000,000		$ 250,000,000
One month LIBOR rate spread [Domain] \| New Credit Agreement
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate				1.00%
Covenant Relief Period [Domain] \| New Credit Agreement
Debt Instrument [Line Items]
Debt Instrument, Fee				0.01
Letter of Credit [Member] \| New Credit Agreement
Debt Instrument [Line Items]
Outstanding letter of credit		93,700,000		$ 93,700,000
Letter of Credit [Member] \| Financial Standby Letter of Credit [Member]
Debt Instrument [Line Items]
Outstanding letter of credit		$ 7,700,000		$ 7,700,000